Flex中利用FileReference类下载文件的例子

接下来的例子演示了Flex中如何利用Flash播放器的FileReference类(flash.net.FileReference)，从服务器端下载文件到本地。在这个例子中，同样还可以了解DataGrid中通过设置

showDataTips属性为True并且在
dataTipField
列中指定一个值。

让我们先来看一下Demo（

可以右键View Source或点击这里察看源代码

）

：
Download: main.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="vertical"
verticalAlign="middle"
backgroundColor="white"
creationComplete="init();">

<mx:Script>
<![CDATA[
import mx.controls.Alert;
import mx.collections.ArrayCollection;
import flash.net.FileReference;

[Bindable]
[Embed('assets/disk.png')]
private var diskIcon:Class;

[Bindable]
private var arrColl:ArrayCollection;

/* URL of the file to download. */
private const FILE_URL:String = "http://blog.minidx.com/ext/downloading-files-in-flex-using-the-filereference-class/srcview/main.zip";

private var fileRef:FileReference;
private var urlReq:URLRequest;

private function init():void {
/* Initialize the array collection to an empty collection. */
arrColl = new ArrayCollection();

/* Set up the URL request to download the file specified by the FILE_URL variable. */
urlReq = new URLRequest(FILE_URL);

/* Define file reference object and add a bunch of event listeners. */
fileRef = new FileReference();
fileRef.addEventListener(Event.CANCEL, doEvent);
fileRef.addEventListener(Event.COMPLETE, doEvent);
fileRef.addEventListener(Event.OPEN, doEvent);
fileRef.addEventListener(Event.SELECT, doEvent);
fileRef.addEventListener(HTTPStatusEvent.HTTP_STATUS, doEvent);
fileRef.addEventListener(IOErrorEvent.IO_ERROR, doEvent);
fileRef.addEventListener(ProgressEvent.PROGRESS, doEvent);
fileRef.addEventListener(SecurityErrorEvent.SECURITY_ERROR, doEvent);
}

private function doEvent(evt:Event):void {
/* Create shortcut to the FileReference object. */
var fr:FileReference = evt.currentTarget as FileReference;

/* Add event order and type to the DataGrid control. */
arrColl.addItem({data:arrColl.length+1, type:evt.type, eventString:evt.toString()});

try {
/* Update the Model. */
fileRefModel.creationDate = fr.creationDate;
fileRefModel.creator = fr.creator;
fileRefModel.modificationDate = fr.modificationDate;
fileRefModel.name = fr.name;
fileRefModel.size = fr.size;
fileRefModel.type = fr.type;
/* Display the Text control. */
txt.visible = true;
} catch (err:*) {
/* uh oh, an error of sorts. */
}
}

private function downloadSourceCodeZip():void {
/* Clear existing array collection. */
arrColl = new ArrayCollection();
/* Hide the Text control. */
txt.visible = false;
/* Begin download. */
fileRef.download(urlReq);
}

private function showAlert(item:Object):void {
Alert.show(item.eventString, item.type);
}
]]>
</mx:Script>

<mx:Model id="fileRefModel">
<file>
<creationDate>{""}</creationDate>
<creator>{""}</creator>
<modificationDate>{""}</modificationDate>
<name>{""}</name>
<size>{""}</size>
<type>{""}</type>
</file>
</mx:Model>

<mx:Button id="downloadBtn" label="Download example source code" icon="{diskIcon}" click="downloadSourceCodeZip()" toolTip="{FILE_URL}" height="40" />

<mx:DataGrid id="debug" dataProvider="{arrColl}" width="{downloadBtn.width}" rowCount="5" rowHeight="22" itemClick="showAlert(event.currentTarget.selectedItem)">
<mx:columns>
<mx:DataGridColumn dataField="data" headerText="#" width="20" />
<mx:DataGridColumn dataField="type" headerText="Type" showDataTips="true" dataTipField="eventString" />
</mx:columns>
</mx:DataGrid>

<mx:Text id="txt" condenseWhite="true" visible="false">
<mx:text>
creationDate: {fileRefModel.creationDate}
creator: {fileRefModel.creator}
modificationDate: {fileRefModel.modificationDate}
name: {fileRefModel.name}
size: {fileRefModel.size}
type: {fileRefModel.type}
</mx:text>
</mx:Text>

</mx:Application>